Re: copy partition from a remote server
On Saturday 09 April 2005 00:32, Alex Malinovich wrote:
>On Sat, 2005-04-09 at 05:59 +0200, Frederic Guillet wrote:
>> i want to run a daily back-up of an entire HD (160GO) remotely.
>> Do you know any tool that can perform this on an incremental
>rsync. That's almost EXACTLY what it's made for in the first place.
>It'll compare the checksums for remote files to local files and only
>transfer changes. (Meaning that if you've only changed 1MB worth of
> data in your 160GB HD, it'll only transfer 1MB of data +
> communication overhead.)
rsync works great, but it does have an achilles heel not everyone is
aware of. It works by compareing the local files checksum on a block
of data with the checksum of the same block on the remote machine. I
they match, the remote machine is sent after the next block, and that
block is copied locally from the real file to a temp file, beaucoup
faster than the net copy. When it reaches the end of the file, the
local file is deleted, and the temp copy is renamed in its place.
Now, do you see the achilles heel? You need scratchpad space at least
as large as the largest file you are rsyncing. If you have files
that are multigigabyte, like some dvd images then it needs that same
amount of scratchpad space on the target drive. In other words, its
time to build a bigger raid when that one gets up around 80-85% full.
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